Re: High Thrust Engines
My question is what is your point? On a toon, you pretty have a constant resistance to the prop since the toon just scoots along.
On a planing hull, you need enough thrust to overcome the hole shot. Once over it you don't need as much power to maintain it as the drag is less.
Merc has a 60 hp Bigfoot with a larger heavy duty 2.3:1 gearbox rather than the standard size gearbox with a 1.64:1. It will accept the same size, and has the potential for turning them at the same speed as the 75 and 90 hp engines......gonna bet they just stuck one of those lower units on a modified 60 hp midsection.
In thinking about it, I guess a 60 bigfoot would hole shoot a heavy planing hull about as easy as a 75 or 90 with about the same pitched prop or a little less. It just wouldn't have the top end that they do.
I mean, I can do the same thing with my 90 hp. I can do a hole shot with the throttle say, 3/4 open. I'll plane out (in time) and run up 20-25 mph like that only using roughly relative hp whereas a 60 on the same boat would do the same thing but would be at WOT.
With the regular 60 and the same rig otherwise, it may not have enough thrust to plane out.
Course I can't help but recollect the OMC V4 lower units on their higher hp engines (after the fat 50's....say in the early '60's timeframe) and they turned small props (for the diameters that came later) at high rpm's and seemed to push ok. I recall test driving a 75 on a 16' MFG and it had plenty of gusto.
So I just don't know, but maybe injected something to think about. One thing I can say, however, a small, high pitched, prop, on a small lower unit, running at high rpm's is very efficient at the higher speeds.......once you get it going.
Mark
